The present invention relates to the field of telescopic rifle scopes, and in particular, to rifle scopes that have an internal or self contained adjustment mechanism for elevation and windage.
In a rifle, adjustment of the point of aim is necessary for two reasons: The rifle scope when it is mounted on the rifle cannot be precisely mounted on the rifle bore and therefore requires an adjustment to align the scope to the rifle. This is called xe2x80x9csighting in the scopexe2x80x9d and is generally done when the scope is mounted on the rifle or when there is some question as to the fidelity of the mount. Secondly, when a bullet is fired from a rifle, it commences falling from the moment that it leaves the rifle barrel due to the force of gravity. Consequently, if a rifle scope were not adjustable in the field for distance then a bullet might not strike a distant target, but would likely pass below the target by the distance the bullet has fallen. Accordingly, modern rifle scope design permits adjustment of the scope to compensate for the distance through which a bullet will fall before it reaches a target. This scope adjustment for vertical fall of the bullet is known as xe2x80x9choldoverxe2x80x9d or xe2x80x9celevationxe2x80x9d. The internal lens of the scope are moved so that a new optical path is created which takes in the xe2x80x9choldoverxe2x80x9d adjustment. As a result of the adjustment of the scope, the shooter is able to simply aim at the target through the scope so that the target falls within the crosshairs, and then fire, without having to otherwise take into account the distance through which the bullet will fall in traveling to the target.
A similar horizontal adjustment of the scope allows compensation for sideways movement of the bullet caused by wind. This sideways adjustment is known as a xe2x80x9cwindagexe2x80x9d adjustment.
For adjustment of the scope, many scopes use a rotating knob or dial that is located in the middle section of the scope tube and orientated horizontally and vertical to the longitudinal axis of the scope. The dial is divided or segmented about its axis such that the xe2x80x9cclickxe2x80x9d mechanism provides an audible or tactile indication for every increment of rotation of a dial that is used to adjust the scope for elevation or windage. That is, the shooter makes the adjustment to the scope by observing where the bullet is impacting relative to the crosshairs of the scope and turning the adjustment dial a calculated number of clicks in the correct direction. Since most adjustments are incremented at useful segments (xc2xc in at 100 yards or xc2xd cm at 100 meters) it is relatively easy to adjust the bullet impact into the center of the target and the scope crosshairs. In certain scopes, the dial cooperates with a mechanism that causes a jack screw, or other device, to move up or down proportionately with the degree of rotation of the dial depending upon the direction of rotation of the dial. Typically, the jack screw penetrates an outer tube of the rifle scope, and the end of the screw impinges on the outer surface of the inner tube of the scope, in which an erector assembly or lens assembly is mounted. Often, the inner tube is supported in the outer tube and is able to pivot about a pivot axis within the outer tube. Thus, as the jack screw urges against the inner tube, it causes precise controlled pivotal motion of the inner tube within the outer tube thereby adjusting the scope for elevation or windage.
A variety of mechanisms have been used or proposed over the years that include a detent or click feature. One example of such a mechanism is the use of a tubular collar, with longitudinal internal grooves spaced at precise distances apart, and positioned so that they form a pattern centered on the adjustment screw axis that rotates in concert with the adjustment dial of the scope. The mechanism includes a slidably fixed member with a ball at its tip that is urged against the grooves of the collar, so that the device emits an audible and tactile click whenever the dial is rotated and the ball clicks over from a seated position in one groove to a position in the next groove. This kind of mechanism not only requires very precisely machined grooves on an inner surface of a collar, but also a finely machined ball. Both components are subjected to continual wear as the dial is used.
In accordance with the invention, there is provided a detent mechanism for the adjustment of a rifle scope for elevation and windage and a scope including the detent mechanism.
The invention is applicable to a variety of rifle scopes, and in one embodiment, in which the rifle scope includes an outer tube within which an inner tube containing optical elements is pivotally mounted, the detent mechanism includes mechanical components that provide a tactile and/or audible click when the rifle scope is adjusted by controlled movement of the inner tube. The detent mechanism of the invention includes a spring with a central opening and at least one detent ridge on an upper surface of the spring. The spring is located in, and prevented from rotational movement in, the socket of the outer tube of the rifle, and has a bias force directed away from a base of the socket. A jack screw passes through the opening of the spring and extends into a slot at the base of the socket, to contact the inner tube of the rifle scope. The screw is prevented from rotational movement in the slot. A jack nut threadingly engages the jack screw, and has a frontal face that includes a series of precisely spaced radially extending grooves that are sized to cooperate with the detent ridges of the spring. Thus, the spring urges its upper surface against the face of the nut with sufficient force to urge a detent ridge into a registering groove of the nut. As the nut rotates, when the rifle scope is adjusted, a groove enters a detent ridge with an audible and tactile click, while the jack screw moves up or down thereby urging the inner tube and adjusting the optics of the rifle scope.
The adjustable rifle scope of the invention provides many advantages. Among these being reduced mechanical wear, simplified manufacture and reduced cost relative to some of the commercially available adjustable rifle scopes.